1. Technical Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a backlight driver circuit and an LCD device having the same, in which a forward driving current is applied to red (R), green (G), and blue (B) backlights, thereby improving brightness variation in response to a forward voltage Vf applied to a light emitting diode (LED).
2. Related Art
In general, a color liquid crystal display (LCD) device includes: an LCD panel having an upper substrate, a lower substrate, and a liquid crystal disposed between the upper and lower substrates; a driver circuit for driving the LCD panel; and a backlight for emitting light toward the LCD panel. Such an LCD device is classified as either a color filter LCD or a field sequential LCD according to the manner in which a color image is displayed.
In the color filter LCD, one pixel is divided into R, G and B sub-pixels. In this regard, R, G and B color filters are arranged on the R, G and B sub-pixels, respectively. Thus, light is emitted from one backlight to the R, G and B color filters through the liquid crystal, thereby displaying a color image.
In the field sequential LCD, R, G and B backlights are arranged on one pixel that is not divided into R, G and B sub-pixels, unlike the color filter LCD. In this regard, three primary lights of R, G and B are emitted from the R, G and B backlights, respectively, toward one pixel through the liquid crystal in a time-division manner, thereby utilizing persistence of vision to display a color image.
In the backlight driver circuit of the field sequential LCD, the same driving voltage of 4V is applied even though the R, G and B light emitting diodes are driven by different driving voltages Vf. In this regard, since the same driving voltage is supplied during three sub-frames corresponding to one frame for driving the R, G and B light emitting diodes, the driving voltage generator should generate the highest driving voltage among the driving voltages needed for the R, G and B light emitting diodes, and thus power consumption increases.
Furthermore, since the forward driving voltages supplied to the R, G and B light emitting diodes in each sub-frame vary with temperature, the brightness of each backlight also varies somewhat with temperature, thereby upsetting white balance.